It is known, as for example from earlier commonly owned patent application Ser. No. 191,024 filed Sept. 26, 1980, to twist together a pair of yarns by pulling the yarns off superposed concentric yarn packages carried on a spindle. This spindle extends along an upright axis, has an upper end and a rotatable lower end, and is formed with a passage opening axially upwardly at the upper end and radially outwardly at the lower end. This spindle is driven for rotation about its axis while the yarn packages or bobbins are rotatably carried on a bobbin support that is carried on the spindle between its ends. The bobbin support is prevented from rotating while the spindle is rotated, with the two filaments pulled off the respective yarn packages passing axially down through the passage and radially out through its lower passage end, then up axially around the bobbin support to form a so-called balloon around the bobbin support.
Such an apparatus can relatively easily twist together two yarns to form a thread suitable for knitting or weaving. The two yarns can be of opposite twist so that the resultant thread has a tensile strength substantially greater than the sum of the tensile strength of the two yarns.
The disadvantage of this system is that it is necessary to use standard yarn packages that can be slipped axially down over the spindle one atop the other, or to use a yarn package on which two yarns are wound. It is regrettably impossible to use the standard small-diameter bobbins or so-called cops such as are used in a spinning operation. It is therefore normally necessary to rewind the yarn after spinning from the small-diameter bobbin on which it is spun onto a larger-diameter bobbin for use in the twisting apparatus.
Another disadvantage of the known machines is that they must be frequently reloaded. When the supply on one of the bobbins runs out the machine must be shut down and reloaded.